Bird feeders are often used to attract various species of birds. It is oftentimes desirable to provide food only for one or more specific birds of interest. One way to attract a certain type of bird is to supply the bird feeder with the particular type of food the bird enjoys. For example, it is well known that certain birds, such as hummingbirds and orioles, prefer a nectar or nectar-type sweet liquid when feeding.
Prior art bird feeders have sought to prevent access from unwanted heavier birds and rodents such as squirrels. For example, Hornung U.S. Pat. No. 2,230,058 discloses a bird feeder designed for lighter birds. The weight of a heavier bird will lower a feeding platform to a tilted position, thus blocking the seed ports. Additionally, Dehls U.S. Pat. No 4,541,362 discloses a squirrel proof selective bird feeder which utilizes the weight of a squirrel to close off the feeding source by spring actuated means.
Although they target lighter birds, these prior art bird feeders are intended to eliminate heavier birds and rodents from feeding at the bird feeder. However, when the food source is a nectar or sweetened liquid, the biggest problem does not necessarily come from seed feeding birds. The problem often relates to insects, and in particular bees or wasps, which are also attracted to the nectar within the bird feeder. A particularly serious problem is the propensity for bees and other insects to enter and become trapped in the nectar feeder. The insects enter through the feeding ports and are unable to exit once inside the nectar reservoir. The aggregation of bees and other insects is a health hazard for birds, unsightly and a nuisance and, further, may plug or block the feeding ports to a point where it is prohibitive for birds to be able to feed on the nectar.
Brown U.S. Pat. No. 5,269,258 discloses a hummingbird and butterfly feeder which is designed to prevent bees from getting inside. However, certain birds such as orioles which also feed on nectar, lack the long proboscis that the hummingbirds have. The orioles require closer access to the actual nectar and larger feed port openings to get their larger beak into a feeder and in a position to feed. Therefore, bird feeders designed specifically for hummingbirds are problematic in that they tend to exclude large beaked birds.